I received the below error message when I ran this command
ALTER TABLE WAC.SUPPRESSED_ CUSTOMER ALTER COLUMN CUSTOMER_ID SET DATA TYPE VARCHAR(28)

DB21034E The command was processed as an SQL statement because it was not a
valid Command Line Processor command. During SQL processing it returned:
SQL0190N ALTER TABLE "WAC.SUPPRESSED _CUSTOMER" specified attributes for
column "CUSTOMER_I D"...